Increased environmental concerns, including the quality of groundwater has prompted increased government regulations and testing requirements for groundwater supplies. These regulations include requirements relating to the monitoring and sampling of groundwater quality and contamination levels. In response to these regulations, numerous devices have been developed for groundwater sampling and monitoring, such as those described in my prior issued U.S. Pat. Nos. 4,669,554; 5,046,568; 5,449,045; 5,570,747 and 5,669,454.
These devices are commonly known as sampling devices and typically include a drive point having a lower portion configured for penetrating the ground and an upper portion which is removably coupled to a tubular drive point holder or extension tube. An elongated annular drive rod is coupled to an upper end of the tubular drive point holder to extend its length and to facilitate driving of the drive point into the ground. An annular seal between the drive point and the point holder prevents the ingress of groundwater or soil during insertion of the sampling device. An interior pipe extends through the annular drive rod and the tubular drive point holder. This internal pipe includes a fluid passageway at its bottom end which allows groundwater to enter. The groundwater can then be extracted or otherwise accessed for sampling.
In a typical operation, a section of the elongated annular drive rod is coupled to the tubular point holder which is in turn removably coupled to a drive point. The upper end of the annular drive rod is pushed, driven or otherwise forced into the ground to form a borehole. Additional sections of annular drive rods may be sequentially connected together to form a pipe string and increase the depth of penetration. The sampling device eliminates the need for drilling, digging or other well operations as well as the associated need to remove or otherwise handle the displaced soil. These advantages are particularly useful when testing in contaminated soil.
Once the drive point reaches the desired location and depth, the annular drive rod, including the attached tubular point holder and any attached pipe string are withdrawn slightly. This slight retraction causes a portion of the sampling device and particularly, the tubular point holder, to slide upward with respect to the drive point which is frictionally restrained in the ground. This upward sliding motion opens a flow path between the drive point and the retracted tubular drive point holder and permits groundwater to enter the sampling device at the desired depth only. The groundwater is then accessed through the interior pipe to be tested, sampled or otherwise treated. The annular drive rod, including any attached drill string is then removed, leaving the drive point and interior pipe within the ground.
Currently, several manufacturers supply this general type of sampling device. Each manufacturer has their own style and configuration as well as differing sizes. These differing sampling devices, including those having different diameters, are used to creating different diameter boreholes and to accommodate various quantities of groundwater as well as to allow usage with different diameter drive rods. As a result, each manufacturer produces a specific drive point which is sized to couple with each of their specific tubular point holders. However, all of these drive points are commonly configured, including a protruding stub extending from an upper end and an o-ring to provide the frictional connection and the watertight seal against the inner diameter of the tubular point holder.
As a consequence of the above design, the stub and o-ring on each drive point, although commonly configured, will only frictionally and sealably fit into a sampling device having a specific interior diameter. This results in a specifically sized drive point being required for each sampling device size as well as for each sampling device manufacturer. Retailers and users are thus, required to stock numerous different drive points for each of the different sized sampler devices, including those by each manufacturer. These drive points may be substantially identical, with the exception of the stub and o-ring sizes. Operator confusion, down time and additional costs result when the right sized drive point is not available for the sampling device being used. In addition, each user is required to expend a major cost to stock and support the large number and variety of drive points required for the multiple sized sampling devices. There is thus a need for a drive point which could universally fit a large variety of sampling devices and particularly a wide range of tubular point holder diameters.
A number of devices and techniques have been provided for supplying a single drive point which can fit sampling devices of various sizes and configurations. In one such example, the drive point has a stub supporting two spaced apart o-ring grooves. Each of the o-ring grooves is a different size to accommodate a different sized o-ring and thus, seal against point holders of at least two different inner diameters.
In another configuration, an annular shim is placed over the stub to accommodate and seal against a larger diameter point holder. The annular shim is slid over the smaller diameter stub to form a larger outer diameter stub which supports a corresponding larger diameter o-ring. The annular shim accommodates and seals against a point holder having a larger inner diameter.
These configurations, devices and techniques however, have some disadvantages. In general, the stub having the two spaced apart o-ring grooves is difficult to use and only increases the functionality of the drive point slightly. This is due, in part, because o-rings are relatively hard and not sufficiently compressible and expansive to accommodate the various inner diameters of the different tubular point holders. Annular shims are not practical because they just require another component, further frustrating the need to simplify and reduce the overall number of required components. In addition, shims provide an additional path for leakage into the interior pipe before the sampling device reaches the desired location and depth. There is thus a need for a universal drive point device which is capable of frictionally coupling with and sealing against a tubular point holder having a range of inner diameters. There is also a need for such a drive point device which is simple to use and inexpensive to manufacture.